Fuel feed system for carburetors



y 1932. c. c. BRADBURY 1 1,858,388

FUEL FEED SYSTEM FOR CARBURETQRS Filed Sept. '5, 1929 oz zM/md a Bmdmg Patented May 17, 193

CLIFFORD C. IBRADB'U RY, F GLENCOE, ILLINOIS, ASSIGNOR T0 CURTIS 3. GP,

' TRUSTEE, 0F GLENCOE, ILLINOIS FUEL FEED SYSTEM FOR CARJBURETORS Application filed September 3, 1929. Serial No. 389,902.

My invention relates to an improvement over that type of fuel feed system disclosed in my prior Patent 1,364,479 for automatic fuel feed system for carburetors, issued J anuary 4, 1921, wherein I disclosed mechanism for lifting fuel from the main supply tank at a low level to a fuel chamber or secondary supply tank at or above the level of the carburetor, utilizing the depression in pressure produced by engine suction to lift fuel with which air was permitted to co-mingle at the .main supply tank so as to lighten the fuel lift.

My improved fuel feed system for carbulfi retor utilizes a suction for drawing the fuel and air from the low level tank which is greater than engine suction or that suction to which the induction chamber of the carburetor is subjected and which necessitates maintaining a relatively high depression in the closed fuel chamber. The system also embodies means for withdrawing air after it arrives in the fuel chamber. I have found, particularly in warm weather, that boillng of the fuel takes place in carburetors of the fuel lift type, in which the fuel is subjected to a depression in ressure, and that this condition particularly in the region of the fuel chamber near the fuel nozzle, results in formation of gases which pass through the fuel nozzle in slugs, momentarily interrupting the supply of fuel to the induction chamber.

An object of my present invention is to rovide a fuel feed system of the type descrlbed wherein the fuel chamber is closed to the at-. mosphere and maintained under a depression in pressure and in which means is rovided for withdrawing air and ases rom the to chamber so that only liquid uel may pass to the fuelnozzle. Another object is to provide a fuel feed system wherein suction greater than induction chamber depression is employed to withdraw air and gases from the fuel chamber and which suction is greater than the suction employed to withdraw fuel from the fuel chamber to the fuel nozzle.

7 A further object is to provide a fuel feed system which is simple in construction, which has no moving parts, and which may be manufactured at relatively low cost.

In the accompanying drawings forming a part of this application, I have illustrated an embodiment of my improved fuel feed system for carburetors, wherein Fig. ?l is a sectional view of the fuel feed system.

Fig. 2 is a sectional view of a motor vehicle illustrating the relative position between the various parts of the system.

In general, my improved fuel feed system comprises a main fuel supply tank A connected by tubing B to the fuel chamber C of the carburetor D, mechanism E for introducing air at atmospheric pressure to the inlet end of tube B so as to pass along with fuel from tank A to chamber C and an air Venturi tube F having its throat connected with the upper region of chamber 0 for withdrawing the air as it rises in the fuel chamber.

The carburetor D is of the fuel lift type comprising an induction chamber 10, a suction multiplying Venturi tube or nozzle 11 forming the primary air inlet of the carbu retor and a relatively large secondary airinlet 12 through which the major part of the air admitted to the induction chamber passes. A spring actuated secondary air valve 13 serves to maintain the depression in the induction chamber substantially constant. lhis valve. may be regulated by adjustment crease the compression of a spring 15 acting against the major valve spring 16. n air dashpot 17 forms a part of the valve assembly and functions to prevent chattering of the valve by momentary fluctuations in engine suction. W

A butterfly'throttle 18 at the delivery orifice of the induction chamber controls the delivery of fuel mixture to the engine manifold 19 and a similar valve 20 is disposed in the secondary inlet 12 to operate as a choke.

The Venturi tube or fuel 'nozzle 11 is mounted with its delivery orifice 25 extending into the induction chamber 10 and with its inlet orifice 26 exposed to atmosphere. The throat 27 of the enturi communicates of a thumb screw 14 whichdecreases or inby a plurality radial passages 28 with a larger passage 29 terminating in the lower regions of the fuel chamber C. The passage of primary air through the Venturi tube or nozzle caused by induction chamber depression creates a depression at its throat 27 which is greater than induction chamber depression is and suflicient at all times dur- 1ng normal running conditions to lift fuel from a low level tank to the throat of the carburetor.

A fuel valve 30 is disposed in the fuel chamber C and is operated by diaphragm 31, the upper surface of which, is subjected to atmospheric pressure and which forms one .wall of the chamber. A spring 32 tends to maintain the valve 30 closed against its seat 33 but yields upon movement of the diaghragm 31 to admit fuel therethrough. This iaphragm and spring 32 coact to maintain a condition of constant depression in the fuel chamber so that differences in the level of fuel in tank A do not appreciably afi'ect the flow of fuel to Venturi nozzle 11.

The lower end of tube B is open, as shown, at 40 and extends to the lowermost region of tank A. That portion of the tube within the tank has a plurality of perforations 41 in its side wall. A cylindrical casing 42 encompasses the perforated part of tube B and is open at its lower end which lies in a plane common to the lower end 40 of the tube. The u per end of the casing 42 is closed except fhr a small opening 43 having an adjustable needle valve-44 associated therewith for varying thepassage of air through the opening. The needle valve extends exteriorly'of tank A and has a knurled head 45 by means of which it may be adjusted.

The space above the fuel in tank A issubjected to atmospheric pressure through a filler cap and the fuel vapor in this space is free to pass through opening 43 into the casing 42 where it may enter one or more of the openings 41 and join the fuel stream in the form' of bubbles separating the fuel into slugs. This condition greatly reduces the weight of the fuel stream so that but slight depression in the fuel chamber C is necesssiry to lift fuel from tank A to the fuel nozz e.

- Mg purpose in providing more than one of t e o enings 41 is to insure initial entrance 0 air into the fuel stream regardless of the level in tank A. If .the level is of the openings 41 before the air was admit-' ted thereto. As all of the fuel vapor must enter through opening 43 the'number ofopenings 41 through which air or vapor may pass is of no material consequence.

. passage 10 and utilized as a masses The means for withdrawing the air elevatedwith the fuel after it arrives in the fuel chamber C is provided in an air Venturi tube F extending through a side wall of the induction passage 10 having its throatcommunicating with a narrow passage 52, the opposite end of which extends to the upper region of chamber C. A pin 53 is disposed within the passage 52 and is ,of such size as to allow not more than five one thousandths of an inch space between the outer wall of the pin and the inner wall of the passage. This pin is mounted upon a screw threaded plug 54 which is received in a. threaded. socket provided in the wall of the induction passage. I have found that a highly restricted passage such as passage 52 .with its pin 53 o ers extremely high resistance to the passage to the passage of fuel therethrough but relatively low resistance to the passage of air and gas therethrough. This condition permits me to use the passage for withdrawal of air and as from the fuel chamber at a relatively high suction without exhausting but a negligible quantity of fuel, at such time as theair and gas has been completely withdrawn from the chamber. However, what very slight quantity of fuel is drawn through passage 52 to the air venturi is there drawn into the induction part of the fuel mixture.

The suction multiplying property of the air venturi F is greater than that of the fuel venturi or nozzle 11 because admission of fuel to the throat of the fuel venturi exerts a choking effect upon venturi action. This condition does not exist in air venturi F and hence the passage of air from induction passage into the fuel chamber by fuel venturi suction is'nnpossible.

In operation my improved fuel feed system functions to 11ft fuel from tank A which is lightened by admission of air through one or more of the openings 41, depending upon the level of fuel in tank A to the fuel chamber C by virtue of the level of constant depres: sion maintained in the fuel chamber. The. quantity of air admitted to the fuel streami may be controlled by adjustment of the needle valve 44 so that just sufiicient air may be admitted to insure lifting of fuel under operative conditions. It is desirable to use as little of the air in the fuel stream as possible so that its complete withdrawal from the fuel chamber may be insured. As the air is high- .ly charged with fuel vapor it becomes a valuable part of the fuel mixture and is ultimatel used as such.

. As the air arrives in the fuel chamber Cit rises to the top of the chamber and is there withdrawn through passage 52 and 00-mingles with the air passing through air venturi F wheseit is drawn into the induction pas- S e I v urlng all normal operatingconditifis the 1 depression at the inlet of passage 52 is greater than that at the inlet of passage 28 through which fuel is conducted to the fuel nozzle 11.

It is thus impossible for air to seek its way into the fuel chamber or induction passage by virtue of suction exerted by the fuel venturi or nozzle 11.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A fuel feed system for carburetors comprising a low level supply tank, a fuel chamber at substantially the level of the carburetor and connected with said supply tank, means for maintaining the fuel chamber under a depression in pressure to cause the fuel to be lifted thereto, means for admitting air to the fuel at the main supply tank, whereby the fuel may pass to the fuel chamber in slugs, and other means subjecting the air in said fuel chamber to a suction greater than the depression, created by said first means for withdrawing the air from the fuel chamber after the fuel and air has been lifted thereto.

2. In combination, a carburetor having a fuel chamber, a low level main fuel supply tank, a passage interconnecting the supply tank and the fuel chamber, means for maintaining a depression in pressure in the fuel chamber to cause the fuel to be lifted from the low level tank to the chamber, means for admitting small quantities of air to said passage at the low level supply tank to cause the fuel to separate into slugs as it passes there-- through, and means subjecting the air in said fuel chamber to a suction greater than the depressioncreated by said first means for withdrawing the air from said fuel chamber, said last named means including a restricted passage through which the air is withdrawn connecting with the upper region of the fuel chamber.

3. In combination, a carburetor, a. suction multiplying fuel nozzle for the carburetor operable to lift fuel from a low level supply tank, to the level of the carburetor, a fuel passage interconnecting said nozzle with the low level supply tank, means for admitting air in small quantities to the passage at said supply tank, and other means for withdrawing the air from said passage prior to thedelivery of the fuel to the nozzle to subject said air to a suction greater than the suction at said fuel nozzle and after the fuel has been lifted to the level of the carburetor.

a. In combination, a carburetor, a suction multiplying fuel nozzle for the carburetor operable to lift fuel from a low level supply tank to the level ofthe carburetor, a fuel passage interconnecting said nozzle with the low level supply tank, means for admitting air in small quantities to the passage at said supply tank, and other means for withdrawing the air from said passage prior to the delivery of fuel to the nozzle and after the fuel has been lifted to the level of the carburetor, said tank to the level of the carburetor, a fuel passage interconnecting said nozzle with the low level supply tank, adjustable means for admitting air in small quantities to said fuel passage at the low level tank whereby the specific gravity of the fuel column between the supply tank and the carburetor may be lowered at will, and means subjecting said air to a suction greater than the suction at said fuel nozzle for withdrawin said air from said passage prior to the admission of the fuel to said nozzle.

6. In combination, a carburetor having a fuel nozzle comprising a Venturi tube, a closed fuel chamber, alow level supply tank connected with said chamber, said chamber communicating with the throat of said Venturi tube whereby fuel may be drawn through said chamber to the nozzle from the low level supplytank, means for admitting air in small quantities to the fuel at the su ply tank prior to its passage to the fuel cham er, and means subjecting said air to a suction greater than the suction at'said fuel nozzle for withdrawing air-from said fuel chamber prior to the admission of fuel to the fuel nozzle. 1

7. In combination, a carburetor having a. fuel nozzle com rising a Venturi tube, a closed fuel chamber, a low level supply tank connected with said chamber, said chamber communicating with the throat of said Venturi tube whereby fuel may be drawn through said chamber to the nozzle from the low level supply tank, means for admittin air in small quantities to the fuel at the supp y tank prior to its passage to the fuel chamber, and means for withdrawing air from said fuel chamber prior to the admission of fuel to the fuel nozzle, said means being operable to withdraw air at suction greater than the suction created at the throat of the fuel nozzle.

8. In combination, acarburetor having a fuel nozzle, comprising a Ventiur tube, a closed fuel chamber, a low level supply tank connectin with said chamber, a passageway between t e throat of the Venturi tube ,and said chamber for drawing fuel from the low level supply tank through said chamber to said nozzle, means for admitting air in predetermined quantities to the fuel at the supply tank prior to its passage to the fuel chamher, and means including a restricted passage "connecting with the upper region of said chamber to subject the air therein to a suction greater than that created at the throat of the Venturi tube to withdraw said air i eeegsee closed fuel chamber a low level supply tank connectin with ssitl chamber, a passageway between t e throat of the Venturi tube and safi chamber for drawing fuel from the low level supply tank throu h said'chamber to the nozzle, means for a mitting air in predetermined quantities to the fuel at the supply tank prior to its admission to the fuel chamher, and means including e restricted passage 30 connecting with the upper region of said chamber to subject the air therein to a suetion greater than that created at the throat of the Venturi tube to withdraw said air prior to the admission of fuel to the fuel nozzle. In witness whereof, I hereunto subscribe r'ny name this 30th day of Au ust, 1929.

CLIFFORD ,C. B -BURY. 

